VACUTAINER (registered trademark) tubes comprise a tube per se and a self-sealing stoppering or closure means. The closure means is made from a material which, on the one hand, seals the tube so as to prevent the interchange of liquids, gases or microscopic particles between the inside and the outside of the tube and on the other hand may be pierced by a syringe needle so as to admit a blood sample taken from a human or animal blood vessel. To assist in the sampling of the blood, the atmosphere of the VACUTAINER or self-sealing stoppered tube is at a reduced pressure relative to atmosphere. Once the needle as been removed from the closure means, the tube is again automatically sealed by virtue of the composition of the closure means.